The average police response time in the area where I live is about 20 minutes. It varies from place to place, but I would rather be prepared to defend my home and loved ones, than have to wait for the cavalry to arrive. A lot of bad things can happen in just one minute. If the OP has legitimate concerns about the safety of his sister, my advice would be she take whatever measures necessary to protect her children and herself. IMHO, learning to properly and safely handle a 20 gauge shotgun would be an important part of her safety plan.